thinness

The story

1. Old English · inherited fromþynnes“thinness, slightness of density, lack of density, tenuity, fluidity, poverty, feebleness of sight, weakness”
2. Middle English · inherited fromthynnesse
3. English todaythinness

From Middle English thynnesse, from Old English þynnes (“thinness, slightness of density, lack of density, tenuity, fluidity, poverty, feebleness of sight, weakness”), equivalent to thin + -ness.